Drill pipe with vibration dampening liner

ABSTRACT

An instrumented drill pipe including an elastomeric tubular liner secured to the inner surface of a tubular member. The elastomeric liner has an interior surface configured to form a plurality of lobes extending radially inwardly and spaced circumferentially about the liner. An elongated measurement instrument assembly is positioned within the longitudinal passage of the liner and frictionally engaged by the lobes of the liner whereby the instrument is supported in the longitudinal passage of the liner so that vibration imparted to the instrument is absorbed by the liner and fluid is permitted to pass through recesses formed between the lobes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a vibration dampening device, and more particularly, but not by way of limitation, to a tubular member provided with an elastomeric liner for dampening vibration of measurement instrumentation used in downhole drilling operations.

2. Brief Description of Related Art

During the drilling of an oil or gas well, a drill string is rotated from the surface causing a drill bit to cut and crush rock formations with the weight of drill collars assisting in driving the drill bit downward into contact with the underlying rock. Drill collars also act as conduits for the drilling fluids used to lubricate the drill bit and carry cuttings back to the surface. Mud motors and turbines are sometimes employed down-hole to aid the drill bit rotation.

At various points during the drilling process, specialized measurement and telemetry tools can be employed to assess downhole conditions. Methods known in the art include measurement-while-drilling (MWD) and logging-while-drilling (LWD), which methods employ a diverse and evolving range of sensors. These sensors are usually located in the drill string near the drill bit with the derived data from such sources as resistivity, gravity, magnetic and nuclear magnetic resonance measurements being stored in down-hole memory or transmitted to the surface.

While such sensors provide highly useful information about the down-hole drilling environment, vibration due to the drilling process can damage the sensors. An axial load is applied to the drill bit during drilling into underlying formations, and this produces vibrations in the overlying drill string, and vibration can occur due to drill string rotation in a deviated or directional well bore. Also, drilling fluid flow around the tool can initiate harmonic vibrations and side-to-side “slapping” of the tool ensues. While most of these sensors are sufficiently robust to address the vibrations of normal drilling conditions, a variety of attempts have been made to counter the potentially damaging vibrations.

Previous attempts of reducing the effects of vibration on measurement instrumentation in downhole drilling operations have focused primarily on attaching springs or fins to the instrumentation to dampen the vibration imparted to the instrumentation by the drill string. However, due to the nature of the environment in which they are used, these springs and fins are prone to failure. Segments of the springs or fins can break off and become contaminants in the drilling fluid.

In an attempt to overcome the disadvantages of using the fins or springs discussed above, the use of individual elastomeric pads on the inner surface of a drill collar have been suggested. While such pads function to support the instrumentation and to dampen vibration, because the pads are secured to the drill collar as individual units, the pads are not interconnected to any other pad, and thus the interface between the pad and drill collar is exposed to the harsh downhole conditions which makes the pads more susceptible to damage or even dislodgement from the drill collar. If damaged or dislodged, the instrumentation which is being supported by the pads may strike the interior surface of the drill collar in a manner that damages the instrumentation.

To this end, a need exists for an improved instrumented drill pipe which is able to effectively protect measurement instrumentation situated in a drill string and which is durable against downhole conditions. It is to such an apparatus that the present invention is directed.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic view of a drilling assembly.

FIG. 2 is a vertical cross-sectional view of an instrumented drill pipe constructed in accordance with the present invention.

FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 2.

FIG. 4 is a cross-sectional view taken along line 3-3 of FIG. 2 with the measurement instrument assembly removed.

FIG. 5 is a vertical cross-sectional view of another embodiment of an instrumented drill pipe constructed in accordance with the present invention.

FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 5.

FIG. 7 is the cross-sectional view of FIG. 6 shown with a measurement instrument assembly supported therein.

FIG. 8 is a cross-sectional view of a tubular member with a mold shown therein for constructing the instrumented drill pipe of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, and more particularly to FIG. 1, a drill string 10 is shown suspended in a wellbore 12 and supported at the surface 14 by a drilling rig 16. The drill string 10 includes multiple joints of drill pipe 18 coupled to a downhole tool assembly 20. The downhole tool assembly 20 includes multiple drill collars 22, an instrumented drill pipe 23, a mud motor 24, and a drill bit 26.

The drill bit 26 is rotated by the mud motor 24 which responds to the flow of drilling fluid, or mud, which is pumped from a mud tank (not shown) through a central passageway of the drill pipe 18, drill collars 22, the instrumented drill pipe 23, and then to the mud motor 24. The pumped drilling fluid jets out of the drill bit 26 and flows back to the surface through an annulus formed between the drill string 10 and the wellbore 12. The drilling fluid carries debris away from the drill bit 26 as the drilling fluid flows back to the surface. The drill collars 22 provide a means to provide weight on the drill bit 26 while maintaining the drill pipe 18 in tension, enabling the drill bit 26 to crush and cut the formations as the mud motor 24 rotates the drill bit 26.

As drilling progresses, it is desirable to monitor a variety of downhole conditions. To accomplish this, an elongated measurement instrument assembly 28 (FIG. 2) is used to measure downhole parameters and formation characteristics. The data can be transmitted in real time utilizing mud pulse and electromagnetic telemetry or recorded in downhole memory and retrieved after the tool returns to the surface.

Referring now to FIGS. 2-4, the instrumented drill pipe 23 includes a tubular member 30, an elastomeric liner 32 which lines the tubular member 30, and the measurement instrument assembly 28 housed within the tubular member 30 and supported by the liner 32. The measurement instrument assembly 28 may be any type of instrument used to acquire measurements downhole, such as a measurement-while-drilling (MWD) tool assembly. During downhole drilling operations, the measurement instrument assembly 28 takes various measurements from within the tubular member 30. Downhole measurement-while-drilling (“MWD”) sensors can be included in the measurement instrument assembly 28 to measure and transmit data during downhole drilling operations. Other types of measurement instrument tools that may be housed in the tubular member 30 include logging-while-drilling (“LWD”), gamma sensors, single shots, steering tools, drift tools, electromagnetic tools. Because accurate measurements are desirable near the bit 26, the instrument assembly 28 is preferably positioned close to the bit 26. However, as discussed above, the interaction of the bit 26 with the adjacent rock formation induces significant vibration to the drill string 10, including the measurement instrument assembly 28, thus the need for a device which dampens the vibration.

The tubular member 30 is shown herein to be a drill collar. However, it will be appreciated that the tubular member may be any type of pipe used in the drilling process. The tubular member 30 has an outer surface 34 and an inner surface 36. The tubular member 30 may have an upper threaded box 37 and a lower threaded pin 38. By way of example, the outer diameter of the tubular member 30 may be about 4.75 inches and the inner diameter may be about 2.81 inches so as to comply with industry standards for a drill collar. The tubular member 30 may also be constructed of varying lengths, but it is generally desirable that the tubular member 30 have a length that also complies with industry standards. For example, a drill pipe or drill collar will typically have a length of about thirty feet when used in the process of drilling a wellbore.

The tubular member 30 is preferably fabricated of a nonmagnetic nickel-copper alloy or other nonmagnetic alloy. This allows certain types of instrumentation, such as a magnetic survey tool, to function without significant interference from the tubular member 30. Alternatively, when magnetism is not an issue, the tubular member 30 may be fabricated of carbon steel or any other material suitable for downhole drilling operations.

The liner 32 is secured to the inner surface 34 of the tubular member 30. The liner is generally tubular in shape and has a first end 39, a second end 40, and an interior surface 42 defining a longitudinal passage 44 (FIGS. 3 and 4) through the liner 32. The interior surface 42 is configured to form a plurality of lobes 46 extending radially inward. The lobes 46 are spaced circumferentially about the liner 32 so as to define plurality of recesses 48 there between and the lobes 46 are interconnected to one another by linking sections 49. The instrument assembly 28 is positioned within the longitudinal passage 44 of the liner 32 and is frictionally engaged by the lobes 46 of the liner 32 whereby the measurement instrument assembly 28 is supported in the longitudinal passage 44 of the liner 32 and vibration imparted to the measurement instrument assembly 28 is absorbed by the liner 32 while permitting drilling fluid to pass through recesses 48 formed between the lobes 46.

As shown in FIG. 2, the liner 32 extends substantially the length of the tubular member 30. However, the length of the liner 32 may be varied so long as the liner 32 functions to support an measurement instrument assembly and dampen vibration imparted to the measurement instrument assembly. In the embodiment illustrated in FIGS. 2-4, each of the lobes 46 of the liner 32 extends from the first end 38 to the second end 40 of the liner 32 in a substantially parallel relationship to the longitudinal axis of the tubular member 30. As such, to properly support the measurement instrument assembly 28, it is preferred that the liner 32 have at least three lobes equally spaced about the liner 32. The liner 32 is fabricated as a unitary member from an elastomeric material that is suitable for the conditions in downhole drilling operations, such as a nitral elastomer.

The lobes 46 and the recesses 48 are dimensioned to provide support to the measurement instrument assembly 28, while allowing a sufficient quantity of drilling fluid to flow through the measurement instrument assembly 28. Additionally, the lobes 46 and the recesses 48 are configured to resist erosion. For example, the lobes 46 and the recesses 48 may be parabolic in shape, with a seamless transition between the lobes 46 and the linking sections 49.

Referring now to FIGS. 5-7, another embodiment of a liner 60 is shown secured within a tubular member 30 a. The liner 60 has a first end 62, a second end 64, and an interior surface 66 defining a longitudinal passage 68 through the liner 60. The interior surface 66 is configured to form a plurality of lobes 70 extending radially inward toward a central axis. The lobes 70 are spaced circumferentially about the liner 60 so as to define plurality of recesses 72 there between, and the lobes 70 are interconnected to one another by linking sections 73. The measurement instrument assembly 28 is positioned within the longitudinal passage 68 of the liner 60 and is frictionally engaged by the lobes 70 of the liner 60 whereby the measurement instrument assembly 28 is supported in the longitudinal passage 68 of the liner 60 and vibration imparted to the measurement instrument assembly 28 is absorbed by the liner 60 while permitting drilling fluid to pass about the measurement instrument assembly 28.

As shown in FIG. 5, the liner 60 extends substantially the length of the tubular member 30 a. However, the length of the liner 60 may be varied so long as the liner 60 functions to support an measurement instrument assembly and dampen vibration imparted to the measurement instrument assembly. In the embodiment illustrated in FIGS. 5-7, each of the lobes 70 of the liner 60 extends from the first end 62 to the second end 64 of the liner 60 in a helical pattern. By forming the lobes 70 in a helical pattern, the measurement instrument assembly 28 is circumferentially supported along all sides of the measurement instrument assembly 28 rather than only along longitudinal lines of contact. As such, the measurement instrument assembly 28 (FIG. 7) is not susceptible to migrating between the lobes 70 as may occur with longitudinally parallel lobes as described above.

The pitch of the lobes 70 (longitudinal distance required for one lobe to make a 360 degree revolution) may be varied. However, it is preferred that the pitch of the lobes 70 not be such that the flow of drilling fluid be significantly impeded. By way of example, the pitch of the lobes 70 may be in a range of from about 40 inches to about 80 inches, and preferably about 60 inches to provide effective support to the measurement instrument assembly 28 while also permitting the passage of drilling fluid though about the measurement instrument assembly 28.

The liner 60 is shown in FIGS. 5-7 to have three lobes 70. However, it should be appreciated that because of the helical pattern of the lobes 70, if desired the liner 60 may be formed to have only one lobe so long as the pitch of that lobe is such that it provides adequate support to the measurement instrument assembly 28. The liner 60 is fabricated as a unitary member from an elastomeric material that is suitable for the conditions in downhole drilling operations, such as a nitral elastomer.

The liners 32 and 60 are each formed similar to the process for manufacturing a stator for a mud motor. The process for forming the liner 32 will be described with reference to FIG. 8. A mold 74 in the shape of the desired longitudinal passage is supported in the tubular member 30. The mold 74 is desirably made of a material which is resistant to heat deformation resulting from the curing process. Additionally, because the mold must be removed, the mold 74 desirably does not adhere easily to the elastomeric material.

A bonding agent is applied to the inner surface of the tubular member 30 so that the elastomeric material readily adheres to the inner surface of the drill collar 30. However, friction alone can also be used to keep the elastomeric material in place within the drill collar 30.

The mold 74 is placed inside the drill collar 30 such that the mold 74 is substantially centered about the longitudinal centerline of the drill collar 30. This may require the use of one or more spacers (not shown). Alternatively, the mold 74 may be shaped to accomplish this without the use of any spacers.

When the mold 74 is positioned within the drill collar 30, a cavity 76 is created between the mold 74 and the inner surface of the drill collar 30. The shape of the cavity 76 is the same as the desired shape of the liner 32, such that when the elastomeric material is inserted into the cavity 76, the elastomeric material takes on the shape of the liner 32. Heat is applied, allowing the elastomeric material to become liquified, and occupy the cavity 76 fully. Once the cavity 76 is occupied by the elastomeric material, the elastomeric material is allowed to set and adhere to the inner surface of the tubular member 30.

Once the liner 32 has been formed, the mold 74 is removed from the drill collar 30, leaving the liner 32 attached to the inner surface of the drill collar 30. In forming the liner 60, removal of the mold requires that the mold be rotated out of the liner 60.

After use of the device 10 over a period of time, the liners 32 and 60 may need replacement. This can occur because of wear, because of a different desirable configuration of the elastomeric lobes and recesses, or for any number of other reasons. When replacement of the liner 32 or 60 is desired, the liners may be removed from the drill collar 30 and replaced with new liners. One method of removal is to drill the liner out of the drill collar 30. However, other methods of removing the liner may be used, such as burning or melting. The liner is then replaced using the process described above.

From the above description, it is clear that the present invention is well adapted to carry out the objects and to attain the advantages mentioned herein, as well as those inherent in the invention. While presently preferred embodiments of the invention have been described for purposes of this disclosure, it will be understood that numerous changes may be made which will readily suggest themselves to those skilled in the art and which are accomplished within the spirit of the invention disclosed and as defined in the appended claims. 

1. An instrumented drill pipe, comprising: a tubular member having a first end, a second end, an outer surface, and an inner surface, the first end and the second end connectable to adjacent tubular members; an elastomeric liner secured to the inner surface of the tubular member, the elastomeric liner being tubular in shape and having a first end, a second end, and an interior surface defining a longitudinal passage through the liner, the interior surface having a plurality of lobes extending radially inwardly and spaced circumferentially about the liner, the lobes defining a plurality of recesses therebetween; and an measurement instrument assembly positioned within the longitudinal passage of the liner and frictionally engaged by the lobes of the liner whereby the measurement instrument assembly is supported in the longitudinal passage of the liner so that vibration imparted to the measurement instrument assembly is absorbed by the liner and fluid is permitted to pass through the recesses formed between the lobes.
 2. The instrumented drill pipe of claim 1 wherein each of the lobes of the liner extends from the first end to the second end of the liner in a substantially parallel relationship to the longitudinal axis of the tubular member.
 3. The instrumented drill pipe of claim 2 wherein the liner extends from the first end of the tubular member to the second end of the tubular member.
 4. The instrumented drill pipe of claim 2 wherein the elastomeric liner has at least three lobes.
 5. The instrumented drill pipe of claim 1 wherein each of the lobes of the liner extends from the first end to the second end of the liner in a helical pattern.
 6. The instrumented drill pipe of claim 5 wherein the liner extends from the first end of the tubular member to the second end of the tubular member.
 7. The instrumented drill pipe of claim 1 wherein the tubular member is non-magnetic.
 8. The instrumented drill pipe of claim 1 wherein the tubular member is a drill collar.
 9. An instrumented drill pipe, comprising: a tubular member having a first end, a second end, an outer surface, and an inner surface, the first end and the second end connectable to adjacent tubular members; an elastomeric liner secured to the inner surface of the tubular member, the elastomeric liner being tubular in shape and having a first end, a second end, and an interior surface defining a longitudinal passage through the liner, the interior surface configured to form a plurality of lobes radially inwardly extending lobes, the lobes spaced circumferentially about the liner so as to define plurality of recesses there between and each lobe extending from the first end to the second end of the liner in a helical pattern; and an measurement instrument assembly positioned within the longitudinal passage of the liner and frictionally engaged by the lobes of the liner whereby the measurement instrument assembly is supported in the longitudinal passage of the liner so that vibration imparted to the measurement instrument assembly is absorbed by the liner and fluid is permitted to pass through the recesses formed between the lobes.
 10. The instrumented drill pipe of claim 9 wherein the liner extends from the first end of the tubular member to the second end of the tubular member.
 11. The instrumented drill pipe of claim 9 wherein the tubular member is non-magnetic.
 12. The instrumented drill pipe of claim 9 wherein the tubular member is a drill collar. 